A multi-chip system may include one or more printed circuit boards with multiple integrated circuits (ICs). In a System-on-Chip (SoC), a system may be integrated into a single IC. An SoC may offer advantages such as higher performance, lower power consumption, and smaller volume and weight, when compared to a multi-chip system.
An SoC may include a number of embedded cores and memory arrays. The inputs to an embedded core, e.g., the core terminals, may not be directly connected to pins on the SoC. The lack of direct access to an embedded core's terminals may complicate testing of the embedded core. A test access mechanism may be used to link a test pattern source to an embedded core's input terminals and to link the embedded core's output terminals to a test pattern sink.